Long popular in the rock world, John Flansburgh and John Linnell are now big with kids too

Linnell, left, and Flansburgh with the on-camera alter egos that appear on their videos.

INDIE HITS Want a hot idea for a popular rock song? How about one that deals with mammalian metabolism? No? What about particle physics or James K. Polk? Such improbable topics have made They Might Be Giants a phenomenon in the indie-rock world for more than 20 years--and that same sense of curiosity and ingenuousness is now making them just as popular with kids.

The core members of the band based in Brooklyn, N.Y.--John Flansburgh and John Linnell, both 48--may have toughened their hides in the same unglamorous venues that all indie groups do, but they brought with them a gentler...